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Topic: Envelope detector

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 Envelope (disambiguation) - Wikipedia, the free encyclopedia
An envelope is a thin paper container formed by folding a sheet of paper and securing the edges, and is the major staple consumable of a letterpost service.
An envelope is a mathematical curve, surface, or higher dimensional object defined as being tangent to a given family of lines or curves (or surfaces, or higher dimensional objects, resp.).
An envelope is a curve that bounds another curve or set of curves, as the modulation envelope of an amplitude-modulated carrier wave in electronics.
en.wikipedia.org /wiki/Envelope_(disambiguation)   (265 words)

 Envelope detector -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-29)
An envelope detector is a device which is used to (additional info and facts about demodulate) demodulate AM signals.
To construct a diode detector, simply connect a (A semiconductor that consists of a p-n junction) diode between the input and output of a circuit, and connect a resistor and capacitor in parallel from the output of the circuit to the ground.
An envelope detector can also be constructed to use a precision rectifier feeding into a (additional info and facts about low-pass filter) low-pass filter.
www.absoluteastronomy.com /encyclopedia/e/en/envelope_detector.htm   (386 words)

 Legal Envelope   (Site not responding. Last check: 2007-10-29)
Any handmade envelope is effectively a lettersheet because prior to the folding stage it offers the opportunity for writing a message on that area of the sheet which after folding becomes the inside of the face of the envelope.
Some envelopes are designed to be reused as the return envelope, saving the expense of including a return envelope in the contents of the original envelope.
But although the paper from which these first machine-made envelopes were made was cut to the shape of a rhombus or diamond and creased ready for folding to form a rectangular enclosure, it did not have the edges of the overlapping flaps treated with a paste or adhesive.
www.wwwtln.com /finance/114/legal-envelope.html   (1470 words)

 United States Patent Application: 0040217807
A temperature compensated diode detector as claimed in claim 16, wherein said diodes of the detecting network and said diodes of the divider network are formed on a single substrate.
A temperature compensated diode detector as claimed in claim 33 wherein the detector network and the divider network are coupled in series, and an output is taken from a junction therebetween.
The temperature compensation is achieved by having a signal path extending through the envelope detector to one input of a differential amplifier, and having a similar reference path using similar diodes extending to the other input of the same differential amplifier.
appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&s1="20040217807".PGNR.&OS=DN/20040217807&RS=DN/20040217807   (4619 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
The input to an envelope detector in a system in accordance with an embodiment of the invention is a voltage but the output of the envelope detector may be a current.
The lower limits of envelope detection are determined by the more dominant of two effects: The first effect is caused by the inability of amplified high-frequency signals to exceed the dead-zone created by exponential nonlinearities in the rectifier.
The envelope detector system as claimed in claim 1, wherein said system further includes a peak detector circuit that is coupled to said rectifier output node.
www.wipo.int /cgi-pct/guest/getbykey5?KEY=05/11106.050203&ELEMENT_SET=DECL   (6452 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
The envelope detection circuit 34 is responsive to the amplified received signal 26 to generate the envelope signal 28.
Accordingly, pulse energy values produced by the energy detector 36 may be higher than a value corresponding to the maximum level of the reception dynamic range causing saturation of the receiver, or may be lower than a level required to distinguish data signals from noise signals.
The pulse energy value produced by the energy detector 36 in response to the pulse 28e is compared by the slicer circuit 38d with the energy detect test level, and step 108 or 110 is repeated depending on whether the pulse energy value is higher or lower than the test level.
www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/79731.001228&ELEMENT_SET=DECL   (4408 words)

 Power- conserving drive-modulation method for envelope-elimination-and-restoration (EER) transmitters - US Patent ...   (Site not responding. Last check: 2007-10-29)
The amplitude (envelope) of the RF output is thereby caused to vary with the supply-voltage input.
Envelope detector 41 is coupled to amplitude modulator 42 the output of which is connected to the supply-voltage input of RF amplifier 44.
Envelope detector 92 is coupled to first amplifier 93 having supply-voltage input 104, and first amplifier 93 is coupled to first filter 94, the output of which is connected to the supply-voltage input of final amplifier 101.
www.patentstorm.us /patents/6256482.html   (8130 words)

 Envelope detector using balanced mixer - Patent 4307347
Envelope detecting means as in claim 1 in which said mixer means comprises a double balanced mixer.
Envelope detecting means as in claim 1 and further comprising filter means responsive to the output signal of said mixer means to remove higher order signal components resulting from mixing said first and second signals.
In accordance with a preferred form of the invention, the signal whose envelope is to be detected is supplied to one input of a mixer.
www.freepatentsonline.com /4307347.html   (2608 words)

 Bat Detectors
The bat detector is one of the most fundamental tools of the researcher into ultrasonic bio-acoustics since it enables direct observation of the acoustic behaviour of an animal whether in the laboratory or in the field.
The simplest form of bat detector is to monitor the waveform from the microphone on an oscilloscope.  This technique is useful for monitoring general activity levels, and with a suitable type of camera can be used to record the signals on film (Griffin 1958).
The frequency divider type of detector is capable of doing this but suffers from the fact that information about the presence of harmonics is lost, and It is not possible to tell whether frequency changes are real or simply shifts of energy from one harmonic to another.
www.brunel.ac.uk /~ibsrjah/batdetectors.htm   (1650 words)

 [music-dsp] 2nd order biquad for envelope detector?   (Site not responding. Last check: 2007-10-29)
One rationale for using a higher-order envelope smoother, would be to use 'pretty short' envelope release, while minimizing ripple in the envelope.
For instance, using a typical first-order IIR attack-release envelope smoother, with a release time of 100 mS-- the wave period of a low-E Bass Guitar string is ~25 mS, so it is pretty obvious the envelope control ripple is gonna be pretty big, causing lots of intermodulation distortion if you use a large compression ratio.
When using a simple first-order IIR envelope smoother, in my experience if you set the envelope release long enough to avoid 'gurgly modulation', the auto-wah is too slow for good effect on fast bass lines.
shoko.calarts.edu /pipermail/music-dsp/2004-May/027162.html   (380 words)

 Signal integrity control technique for an RF communication system - Patent 4998289
The circuit includes a logarithmic envelope detector for receiving a channel's angular modulated signal and for providing a log envelope output signal, a high pass filter for removing a particular range of undesired frequencies from the log envelope output signal, and a level detector for indicating the level of filtered output signal.
More specifically, the logarithmic envelope detector 150 will provide an AC output signal having a magnitude that is directly related to the percentage of amplitude modulation in the envelope of the received (IF) signal regardless of the absolute magnitude of the received (IF) signal.
The (HPF) 152 receives the output signal from the detector 150 to filter out the DC term at the output of the Log envelope detector as well as the low frequency modulation produced by any fading which might be present on the received (IF) signal.
www.freepatentsonline.com /4998289.html   (4702 words)

 [No title]
Their inverse modulator only partially demodulates the envelope by increasing it by +6db on negative peaks and decreasing it by -3.5db on positive peaks and no phase term enters into the equation other than that an interfering signal will add to the envelope but will have little impact on the inverse modulator.
Since the Kahn stereo receiver uses a quadrature synchronous detector and partially demodulates the envelope to reduce distortion why not generate the signal so that the generation is the mathematical inverse of this reception method.
The envelope of the incoming signal is 50% demodulated with a inverse modulator and then detected by a quadrature detector for L-R and 1+L+R is detected with an envelope detector.
www.hal-pc.org /~jsgil/AM-Stereo/ISB.Txt   (3844 words)

 [No title]
For instance, the envelope detector could also be used to drive a "gating" module for noise reduction or for a backwards-tape effect, or to drive the speed of an LFO.
Notice that the envelope detector, Module 7, should be first it the FXBus chain, as it buffers the input signal and redrives the signal into the next FXBus "In" point, and also generates the "SCout" sidechain signal that modulates the filter response of the VCF.
The most obvious uses are to buffer the envelope out or to invert the output of the first opamp to convert to a full-wave rectified envelope detector for smoother results.
www.geofex.com /Article_Folders/FXbus/fxbmod06.htm   (1125 words)

 AM Stereo, How It Works
This process gives the C-QUAM signal a normal AM envelope containing the L+R or monophonic audio, for compatibility with existing monophonic AM radios using envelope detectors, while the L-R stereo difference signal is encoded in the carrier phase.
First, since the envelope of the C-QUAM signal is a faithful copy of the L+R sum signal, an envelope detector is used to recover the L+R sum signal, or monophonic audio.
The L+R sum signal from the envelope detector is then compared, in an error amplifier, with the L+R audio signal coming out of the QUAM synchronous demodulator.
www.geocities.com /CapeCanaveral/9178/radios/amstrjb.html   (791 words)

 [No title]
Not moving away from the envelope detector and reaping the benefits of synchronous detectors is too big a sacrifice to maintain only partial compatibility with envelope detectors.
The first multiplicative process is envelope detection itself because of the non-linear nature of the envelope detector's response to the desired and interfering signals.
Now there is a signal quality detector that is supposed to reduce the amount of cosine correction and other stuff as interference increases so it may be possible to feed the I Det signal back into the Env Det pin when cosine correction is completely disabled if that ever occurs during poor signal conditions.
www.hal-pc.org /~jsgil/AM-Stereo/SynchronousDetection.Txt   (1504 words)

 [music-dsp] Envelope Detection and Hilbert Transform   (Site not responding. Last check: 2007-10-29)
I use the hilbert transform for getting the envelope of wide-band, pulsive signals, such as room impulse response or the cross-correlation function between the input and the output of an electroacoustical system.
However, in some cases, it would be advisable to add some exponential time averaging, for example for emulating the behaviour of an analog RMS meter, such as the RC circuit employed in a sound level meter with "fast" or "slow" time constants.
With 50% overlap, the envelope is "modulated" by the Hanning Wiindows.....
aulos.calarts.edu /pipermail/music-dsp/2004-September/028253.html   (541 words)

 Technology Transfer - Type-based Baseband Predistorter Function Estimation Technique for Nonlinear Power Amplifiers
The invention is based on two important observations: (a) the envelope of a signal with given modulation scheme and pulse shaping function has a unique statistical distribution or “type,” and (b) the response of the power amplifier is continuous (and monotonous for AM to AM) up to its saturation point.
Thus the key to this invention is the use of the distribution function of the modulated signal's envelope at the output of the power amplifier (PA).
The resulting instantaneous envelope is then digitized and fed to a digital signal processor (DSP) where the distribution function of the signal envelope is calculated.
www.crc.ca /en/html/crc/home/tech_transfer/10243?pfon=yes   (488 words)

 Circuits with dynamic biasing - US Patent 6816003   (Site not responding. Last check: 2007-10-29)
an envelope detector for receiving the first input signal for generating a signal representing an amplitude of the first input signal, the second input signal comprising the signal representing the amplitude of the first input signal.
Each of the output signals 2108 is sent into its own envelope detector 2104 which generates a bias control signal 706 for the appropriate portion of the main filter 704.
being the output of the envelope detector of FIG.
www.patentstorm.us /patents/6816003.html   (8216 words)

 [RT] Re: IBOC-QUAM   (Site not responding. Last check: 2007-10-29)
As it is extremely likely that the upper and lower primary and secondary subcarriers of adjacents won't be symmmetrical at the envelope detector, they are a significant source of noise.
A perfect envelope detector will detect the square root of the sum of the I and Q channels squared.
If the I and Q channels are equal, then the vector resolved by the envelope detector will be 1.4 times the I or Q channel.
www.broadcast.net /pipermail/radio-tech/2004-May/053048.html   (404 words)

 Easy Fourier Analysis
Note that the envelope of this signal is not the same as the baseband signal.
Envelope detector can not be used with DSB-SC carrier because the envelope of the DSB-SC signal is not the same as the baseband signal.
Envelope Detector is the simplest and senses the maximum amplitude of the in coming signal which happens to be the message signal.
www.complextoreal.com /base.htm   (3857 words)

 Synchronous Detection in the Sony 7600G
Although envelope detection was used in the old crystal sets and still is used today in most digitally-tuned superhets, synchronous detection is not merely a high-tech frill to add to an already high-tech digitally-tuned receiver.
When a receiver uses an envelope detector, and several of the differently timed signals are among the stronger signals that the receiver "hears", multipath distortion (sometimes called selective fading or QSB) can cause an "in-and-out" effect on the receiver's audio.
Since part of its process is instant-by-instant calculation of the desired signal's carrier frequency and continuously re-tuning the receiver to track the carrier, the synchronous detector compensates, instant-by-instant, for the multipath distortion, and thereby reduces or eliminates the "in-and-out" effect at the receiver's audio output.
www.nyx.net /~dgrunber/7600g.ssi   (696 words)

IIRC, the output of an envelope detector is SQRT(I^2 + Q^2), where I and Q are the in-phase and quadrature components respectively.
The carrier biases the detector to ensure that this positivity constraint is true.) The square root operator, being nonlinear, will cause a certain amount of intermodulation between the I and Q components.
Moreover, because a synchronous detector is linear, there will be no intermodulation between the IBOC sidebands and the analog audio.
www.broadcast.net /pipermail/radio-tech/2004-May/053030.html   (395 words)

 [No title]   (Site not responding. Last check: 2007-10-29)
Assuming that detection is limited only by the variability in the envelope height, Jeffress estimates what he call the effective bandwidth as the width of a filter which when followed by an envelope-height detector would perform as well as the observer.
At the same time the signal from the tape was processed by an electrical detector, which consisted of an RLC (single-tuned) band-pass filter, a square law detector, and an exponential integrator, all followed by a chart recorder.
That is, if one correlated the output of the energy detectors with varying integration times with observer responses, one would probably find that on signal trials an integrator whose integration time is near the duration of the signal correlated best with the observers' responses, but that the longer duration integrators correlated best on noise-only trials.
vision.arc.nasa.gov /personnel/al/papers/67thesis/textnf.htm   (9002 words)

 MATLAB Envelope Detector Simulation   (Site not responding. Last check: 2007-10-29)
An envelope detector is used to demodulate full-AM signals.
The m-file envsim.m can be used to simulate the envelope detector circuit.
The diode is modelled as a switch that is closed when the anode voltage exceeds the cathode voltage.
www.man.ac.uk /Elec/ee3241/envsim.html   (211 words)

 Radio-Electronics.Com :: Radio Receiver AM Demodulation
If the detector is to be used only for detection it does not matter which half of the envelope is used, either will work equally well.
This type of detector or demodulator is called a linear envelope detector because the output is proportional to the input envelope.
Additionally these detectors (demodulators) are susceptible to the effects of selective fading experienced on short wave broadcast transmissions.
www.radio-electronics.com /info/receivers/am_demod/diode_am_demod.php   (572 words)

 (Written by Farial Mahbub)
Frequency modulation encodes data by performing shifting of frequency, phase modulation performs shifts in phase, and amplitude modulation controls the envelope of the carrier wave.
The envelope detector is essentially made up of a rectifier and a low pass filter (see figure below).
Thus, if an input voltage that varies according to the modulation envelope is used, the information present in the sidebands would be successfully recovered.
www.engr.sjsu.edu /rkwok/EE172/Mod-DeMod.htm   (1523 words)

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